Lightweight and solid. barrel nut is machined for an adjustable wrench - Guntec USA Air Lite Honeycomb Series M-LOK Free Floating Handguard w/Monolithic Top Rail

Barrel nut didn't use the standard ar tool, had to use an adjustable crescent wrench. Otherwise, plenty of spots to attach the rail and low diameter make indexing easy. Not an octagon shape, more of a squared off cylinder. Mounted to a billet upper but I think it would look perfect on a forged upper. I got the nine inch for a nine inch barrel, fits perfectly with a 2 chamber muzzle brake. Might look even better with a 10.5